Micro structure and its manufacture method

ABSTRACT

A laminated substrate is prepared, the laminated substrate having two layers including a first film and a second film in tight contact with the first film, the second film being made of a material capable of being etched with synchrotron radiation light. A mask member with a pattern is disposed in tight contact with the surface of the second film of the laminated structure or at a distance from the surface of the second film, the pattern of the mask member being made of a material not transmitting the synchrotron radiation light. The synchrotron radiation light is applied on a partial surface area of the second film via the mask member to etch the second film where the synchrotron radiation light is applied and to expose a partial surface area of the first film on the bottom of an etched area.

This is division of application Ser. No. 09/098,289 filed Jun. 16, 1998now U.S. Pat. No. 6,159,403.

This application is based on Japanese Patent Application No.HEI-9-163148 filed on Jun. 19, 1997, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

a) Field of the Invention

The present invention relates to a micro structure and its manufacturingmethod, and more particularly to micro machines and a manufacturingmethod suitable for fabrication of micro machines.

b) Description of the Related Art

As a manufacturing method for micro structures, techniques ofLithographie Galvanoformung Abformung (LIGA) are known. ConventionalLIGA techniques will be briefly described.

A photoresist film is formed on a conductive support substrate. Thisphotoresist film is locally exposed with X-rays by using a LIGA maskhaving a high contrast, and thereafter developed and patterned. Regionswhere the photoresist film is removed are filled with metal bygalvanizing. As the photoresist film is removed, a micro structure madeof metal can be formed.

With LIGA techniques, it takes generally several hours to expose anddevelop a photoresist film. A photoresist mask having a high contrast isalso required.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method ofmanufacturing a micro structure having a shortened process time.

It is another object of the present invention to provide a compositemicro structure made of a combination of different materials.

According to one aspect of the present invention, there is provided amethod of manufacturing a micro structure comprising the steps of:preparing a laminated substrate of two layers including a first film anda second film in tight contact with the first film, the second filmbeing made of a material capable of being etched with synchrotronradiation light; disposing a mask member with a pattern in tight contactwith a surface of the second film of the laminated structure or at adistance from the surface of the second film, the pattern of the maskmember being made of a material not substantially transmitting thesynchrotron radiation light; and applying the synchrotron radiationlight on a partial surface area of the second film via the mask memberto etch the second film where the synchrotron radiation light is appliedand to expose a partial surface area of the first film on a bottom of anetched area.

Since the second film is etched by applying radiation light, a processtime can be shortened as compared to LIGA techniques which utilizesexposure and development processes.

According to another aspect of the present invention, there is provideda micro structure comprising: a first film made of a material having anetching resistance to radiation light different from an etchingresistance of polytetrafluoroethylene; and a second film in tightcontact with the first film and made of polytetrafluoroethylene, thesecond film being patterned, and a surface of the first film beingexposed in an area where a pattern of the second film is not formed.

By using this micro structure, a micro machine made of plastics can beformed.

According to another aspect of the present invention, there is provideda micro structure comprising: a polytetrafluoroethylene film having athrough hole; and a metal member filling the through hole.

A micro structure can be formed by selecting each material of eachregion of the structure so as to satisfy the mechanical and electricalcharacteristics required for the region.

As described above, it is possible to perform micro processing by usingradiation light. A micro composite material can be formed by filing amicro space in a micro structure with another material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram showing a working system used by theembodiments of the invention, and FIGS. 1B and 1C are schematic crosssectional views of the working system.

FIG. 2 is a front view of a drive mechanism used by the working systemshown in FIGS. 1A to 1C.

FIGS. 3A to 3F are cross sectional views illustrating processes of amethod of manufacturing a micro structure according to a firstembodiment of the invention.

FIGS. 4A to 4C are cross sectional views illustrating processes of amethod of manufacturing a micro structure according to a modification ofthe first embodiment.

FIGS. 5A to 5C are cross sectional views illustrating processes of amethod of manufacturing a micro structure according to a secondembodiment of the invention.

FIGS. 6A to 6C are cross sectional views illustrating processes of amethod of manufacturing a micro structure according to a thirdembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1A is a schematic diagram showing a working system used by a methodof manufacturing a micro structure according to the embodiments. Asynchrotron radiation light (SR light) is emitted along an optical axisof an orbit of electrons accumulated in a synchrotron. A workpiece 4 isplaced at a distance L from the radiation light source on the opticalaxis 5. In front of the workpiece 4, a mask 3 is disposed at a distanceG. The electron orbit 1, workpiece 4 and mask 3 are housed in the samevacuum chamber.

The mask 3 has regions substantially not transmitting SR light andregions substantially transmitting the SR light. A region substantiallytransmitting SR light is a region through which SR light having anintensity strong enough to process the workpiece passes, and a regionsubstantially not transmitting SR light is a region through which SRlight cannot pass or even if it passes, the SR light is attenuated to anintensity not enough to process the workpiece.

The mask used in the embodiments is made of a copper plate of 10 to 100μm in thickness, and has a pattern of a desired micro component. Themask may be made of other metal instead of copper. The thickness of themask may be about 2 to 10 μm.

The SR light 2 is applied to the surface of the workpiece 4. A surfaceregion of the workpiece 4 where the SR light is applied is removedthrough etching. By forming a micro pattern on the surface of the mask3, the surface of the workpiece 4 can be processed to have a micropattern.

FIG. 1B is a cross sectional view of a working unit. In a vacuum chamber20, a sample holding stage 14 is mounted. A workpiece 4 is placed on thesample holding surface of the sample holding stage 14. A mask 3 isdisposed in front of the workpiece 4 by a mask holder 17. The mask 3 maybe set in contact with the surface of the workpiece 4, or spaced aparttherefrom by some distance. In processing the workpiece 4, SR light 2 isapplied from the left side in FIG. 1B to the surface of the workpiece 4through the mask 3.

The sample holding stage 14 is made of, for example, ceramics and has aheater 8 embedded therein. Lead wires of the heater 8 are connected toone ends of terminal 21 which pass through the wall of the vacuumchamber 20, and the other ends of the terminal 21 are connected viacables to a power source 7 which supplies current to the heater 8. Ascurrent flows through the heater 8, the workpiece 4 is heated.

A thermocouple 23 is mounted on the sample holding surface of the sampleholding stage 14. Lead wires of the thermocouple 23 extend via a leadwire output port 22 to the outside of the vacuum chamber 20, and areconnected to a temperature controller 9. The lead wire output port 22 issealed, for example, by solder. This temperature controller 9 controlsthe power source 7 to regulate the amount of current flowing through theheater 8 and set the temperature of the sample holding surface to adesired temperature.

FIG. 1C shows another example of the structure of the sample holdingstage. A gas flow path 16 is formed inside of a sample holding stage 15.Gas at a desired temperature is flowed through the gas flow path 16 toexchange heat with a workpiece 4, to thereby maintain the workpiece at adesired temperature.

FIG. 2 shows a Z-axis direction drive mechanism for a workpiece 4 and amask 3. A sample holding stage 14 is mounted on the drive mechanism 10,with its sample holding surface being set generally perpendicular to anoptical axis direction (Y-axis direction) of SR light 2. The workpiece 4is mounted on the sample holding surface of the sample holding stage 14,and the mask 3 is disposed at a distance G from the surface of theworkpiece 4.

The drive mechanism 10 has handles 11, 12 and 13. As the handle 11 isrotated, the sample holding stage 14 moves in the up/down direction asin FIG. 2 (Z-axis direction). The handle 11 is rotated by using steppingmotor to move the stage at a desired constant speed.

As the handles 12 and 13 are rotated, the sample holding stage 14 movesin a direction vertical to the drawing sheet (X-axis direction) and inthe Y-axis direction. With these handles 12 and 13, the position of thesample holding stage 14 can be minutely adjusted both in the X- andY-axis directions.

As the handle 11 is rotated by using the stepping motor while SR light 2is applied to the surface of the workpiece 4, the workpiece 4 movesalong the Z-axis direction so that a relatively large area can beprocessed with ease.

Next, a method of manufacturing a micro structure according to the firstembodiment of the invention will be described with reference to FIGS. 3Ato 3F.

As shown in FIG. 3A, a substrate 30 is prepared which is a lamination ofa metal film 31 and a polytetrafluoroethylene film 32 tightly coupled tothe metal film 31. For example, the substrate 30 may be formed bydepositing an Ni film and a Cu film through galvanizing on apolytetrafluoroethylene film, or by placing a polytetrafluoroethylenefilm on a Cu plate and heating and pressing to adhere them throughmelting. In this embodiment, the thickness of the metal film 31 is 20 μmand the thickness of the polytetrafluoroethylene film 32 is 300 μm.

A mask member 33 is disposed at a predetermined distance from thesurface of the polytetrafluoroethylene film 32. The mask member 33 is astainless sheet having a plurality of slits of 100 μm in width disposedat an interval of 200 μm.

SR light 2 is applied via the mask member 33 to thepolytetrafluoroethylene film 32. Regions of the polytetrafluoroethylenefilm 32 where the SR light 2 is applied are etched and removed. Sincethe metal film 31 is not etched, the etching stops when the surface ofthe metal film 31 is exposed.

The whole thickness of the polytetrafluoroethylene film 32 of 300 μm inthickness could be etched in about 10 minutes at the substratetemperature of 200° C. through exposure of SR light having a photondensity of about 6×10¹⁵ photons/s·mm². With conventional LIGAtechniques, exposure of about 2 to 3 hours and development of about 2 to3 hours become necessary for a photoresist film having a thickness ofabout 300 μm. In this embodiment, it is possible to process apolytetrafluoroethylene film in a short time.

FIG. 3B shows the surface of the metal film 31 partially exposed. Thepolytetrafluoroethylene film 32 is formed with grooves 35 correspondingto the slits of the mask member 33.

As shown in FIG. 3C, metal such as Cu, Ni and Pt is deposited throughgalvanizing on the surface of the metal film 31 exposed on the bottom ofthe groove 35. The groove 35 is therefore filled with a metal material36 such as Cu, Ni and Pt.

SR light or electron beams are applied to the leftpolytetrafluoroethylene film 32. If SR light is applied, thepolytetrafluoroethylene film 32 is etched, whereas if electron beams areapplied, the polytetrafluoroethylene film 32 deteriorates its qualityand changes to powder-like substances so that thepolytetrafluoroethylene film 32 can be easily removed.

FIG. 3D is a cross sectional view showing the substrate after thepolytetrafluoroethylene film 32 is removed. The metal member 36 is lefton the metal film 31. The metal members 36 are disposed at a pitch of100 μm, each having a width of about 200 μm. A micro structure made of ametal is therefore formed.

As shown in FIG. 3E, a plastics material 37 a is flowed onto the surfaceof the metal film 31 for molding the plastics material 37 a. As theplastics material 37 a is peeled off from the metal film 31, a microstructure 37 made of plastics is formed.

Next, a method of manufacturing a micro structure according to amodification of the first embodiment will be described with reference toFIGS. 4A to 4C.

As shown in FIG. 4A, a metal film 40 made of Cu or the like is depositedto a thickness of 2 to 20 μm on the surface of a polytetrafluoroethylenefilm 32 of a laminated substrate 30 same as that shown in FIG. 3A. Aresist pattern 41 is formed on the metal film 40. The resist pattern 41is formed by coating a resist film and exposing and developing it via aphoto mask. This exposure is performed using visual light or ultravioletlight. The photo mask may be a mask commonly used in this field, such asa glass substrate formed with a Cr pattern.

By using the resist pattern 41 as a mask, the metal film 40 is etched toform openings. After the openings are formed, the resist pattern 41 isremoved.

FIG. 4B is a cross sectional view of the substrate 30 and metal film 40after the resist pattern 41 is removed. Next, SR light 2 is applied tothe surface of the laminated substrate 30. The polytetrafluoroethylenefilm 32 exposed in the openings of the metal film 40 is etched.

FIG. 4C is a cross sectional view of the substrate 30 and metal film 40after the polytetrafluoroethylene film 32 is etched. As the metal film40 is removed, a micro structure similar to that shown in FIG. 3B isformed.

With the method described with FIG. 3A, the mask member 33 is a metalsheet having slits. If it is necessary to make an isolated lightshielded area, the mask member 33 shown in FIG. 3A cannot be used. Insuch a case, another mask member is used which has a membrane made ofmaterial transmitting SR light such as SiC and a pattern made ofmaterial shielding SR light such as Ti formed on the membrane. However,these mask materials are expensive and moreover have a weak mechanicalstrength and are not easy to handle.

With the method shown in FIGS. 4A to 4C, a pattern is transferred to themetal film 40 by using a usual mask for visual light or ultravioletlight. Therefore, this method has advantages of low cost andeasy-to-handle. Furthermore, since the metal film 40 is in tight contactwith the polytetrafluoroethylene film 32, it is easy to form an isolatedlight shielding area.

Next, a method of manufacturing a micro structure according to a secondembodiment of the invention will be described with reference to FIGS. 5Ato 5C.

A laminated substrate 30 shown in FIG. 5A has the same structure as thatof the first embodiment shown in FIG. 3B.

As shown in FIG. 5B, a plastics material 45 a is flowed onto the surfaceof the substrate 30 to mold the plastics material 45 a. As the plasticsmaterial 45 a is peeled off from the substrate 30, a micro structure 45made of plastics is formed as shown in FIG. 5C.

In the first embodiment, the metal film 31 and the micro metal member 36formed on the surface of the metal film 31 by galvanizing are used as amold. Instead, as in the second embodiment, the processedpolytetrafluoroethylene film 32 formed on the surface of the metal film31 may be used as a mold.

In the first and second embodiments, a polytetrafluoroethylene film isused as a material to be processed in a micro shape. Other materialscapable of being etched with SR light may also be used, such ascrystalline materials of NaCl, LiF and the like.

Next, a method of manufacturing a micro structure according to a thirdembodiment of the invention will be described with reference to FIGS. 6Ato 6C.

A laminated substrate 30 shown in FIG. 6A has the same structure as thatof the first embodiment shown in FIG. 3C. The metal film 31 on thebottom of the substrate 30 is removed. If the metal film 31 is made ofCu, it can be removed through etching using, for example, sulfuric acid.While the metal film 31 is etched, the opposite surface of thepolytetrafluoroethylene film 32 is covered with a resist film or thelike.

If an etching selection ratio of the metal film 31 to the metal member36 is small, etching is performed under the control of etching time andstopped when the whole thickness of the metal film 31 is removed. If theetching selection ratio of the metal film 31 to the metal member 36 canbe made large, only the metal film 31 can be easily etched and removedwithout strict time control.

FIG. 6B is a cross sectional view showing the structure of FIG. 6A afterthe metal film 31 is removed. A fine composite material can be formed,with the metal member 36 being filled in the space of thepolytetrafluoroethylene film 32. For example, a composite material canbe formed having a region requiring a resistance to chemicals which ismade of polytetrafluoroethylene and a region requiring a mechanicalstrength or an electrical conductivity which is made of metal.

In the process shown in FIG. 6B, although the metal film 31 is fullyremoved, it may be locally etched.

FIG. 6C shows another structure in which the metal film 31 is locallyetched to leave it locally in an area corresponding to the metal member36 and its circumferential area. By locally etching the metal film 31,adhesion between the polytetrafluoroethylene region and the metal regioncan be enhanced while insulation between respective metal regions ismaintained.

If it is not necessary to ensure insulation between respective metalregions, the metal film 31 is not necessarily removed.

In the above embodiments, the polytetrafluoroethylene film having athickness of about 300 μm is processed. The thickness is not limitedthereto. However, since it takes a long process time if the workpiecebecomes thick, a suitable range of the thickness of a workpiece is notthicker than 3000 μm.

If a micro structure is used as a micro machine, this structure isrequired to have a mechanical strength more or less. It is thereforepreferable to set the thickness of a workpiece to 30 μm or thicker.However, if the micro structure is not required to have a mechanicalstrength, the thickness is not limited.

The present invention has been described in connection with thepreferred embodiments. The invention is not limited only to the aboveembodiments. It is apparent that various modifications, improvements,combinations, and the like can be made by those skilled in the art.

What is claimed is:
 1. A method of manufacturing a micro structure,comprising: preparing a laminated substrate of two layers including afirst film and a second film in tight contact with the first film, thesecond film being made of a material capable of being etched withsynchrotron radiation light; disposing a mask member with a pattern intight contact with a surface of the second film or at a distance fromthe surface of the second film, the pattern of the mask member beingmade of a material which substantially does not transmit the synchrotronradiation light; and applying the synchrotron radiation light on apartial surface area of the second film via the mask member to etch thesecond film and expose a partial surface area of the first film; whereinthe first film is made of a conductive material, and the method furthercomprises: after exposing the partial surface area of the first film,depositing a metal member through galvanizing on the exposed partialsurface area of the first film to fill, with the metal member, a regionwhere the second film has been etched; and applying the synchrotronradiation light or an electron beam to the laminated substrate to removea remaining portion of the second film.
 2. A method according to claim1, wherein the second film is made of polytetrafluoroethylene.
 3. Amethod of manufacturing a micro structure, comprising: preparing alaminated substrate of two layers including a first film and a secondfilm in tight contact with the first film, the second film being made ofa material capable of being etched with synchrotron radiation light;disposing a mask member with a pattern in tight contact with a surfaceof the second film or at a distance from the surface of the second film,the pattern of the mask member being made of a material whichsubstantially does not transmit the synchrotron radiation light;applying the synchrotron radiation light on a partial surface area ofthe second film via the mask member to etch the second film and expose apartial surface area of the first film; and molding a plastic materialusing the first film and portions of the second film left on the partialsurface area on the first film, after exposing the partial surface areaof the first film.
 4. A method according to claim 3, wherein the secondfilm is made of polytetrafluoroethylene.
 5. A method of manufacturing amicro structure, comprising: preparing a laminated substrate of twolayers including a first film and a second film in tight contact withthe first film, the second film being made of a material capable ofbeing etched with synchrotron radiation light; disposing a mask memberwith a pattern in tight contact with a surface of the second film or ata distance from the surface of the second film, the pattern of the maskmember being made of a material which substantially does not transmitthe synchrotron radiation light; applying the synchrotron radiationlight on a partial surface area of the second film via the mask memberto etch the second film and expose a partial surface area of the firstfilm; and after exposing the partial surface area of the first film,depositing a metal member through galvanizing on the exposed partialsurface area of the first film to fill, with the metal member, a regionwhere the second film has been etched; and patterning the first film topartially leave the first film at an area corresponding to the metalmember and a circumferential area of the metal member.
 6. A methodaccording to claim 5, wherein the second film is made ofpolytetrafluoroethylene.